The sitting position you’re describing — knees bent, shins and tops of the feet flat on the ground, with your weight resting on your ankles/heels — is most commonly called “seiza” in Japanese.
- Seiza (正座) literally means “proper sitting” in Japanese culture, and it’s a traditional formal way of sitting.
- In yoga, a very similar position is called Vajrasana (the “thunderbolt pose”).
So in general terms:
- In Japanese context → Seiza
- In yoga context → Vajrasana
- In plain English → “kneeling and sitting back on your heels”